Pneumatic dispatch-tube



Y UNITED STATES PATENT OFFICE.

DAVID HUNTER, 0F AUNNEAPOLIS, MINNESOTA.

PNEUMATIC DISPATCH-TUBE.

SPECTFICATION forming part of Letters I atent No. 468,419, dated February 9, 1892. Application filed August 10, 1891. Serial No. 402,227. (No modelJ 4To @Il rolt/olii.l it 71mgco/toorn:

Be it known that I, Devin lll'iv'rnn, a citizen of the `United States, residingv at Minneapolis, in the county of Hennepin and State oi iliinnesota, have invented certain new and useful Improvements in Pneumatic Dispatchl`ubes; and l do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertaius to make and use the same.

My invention is in the nature ot' an improvement in pneumatic dispatch-tubes of the class shown and described in my pending' application entitled Pneumatic dispatch-tubes,7 tiled lllay 7, 189i, under Serial No. 391,969.

in my present invention, as in said former application, I employ a system of dispatchtubes of the ordinary and well-known type and produce a forced draft orcurrentof airtherethrough by applying a jetof steam to the interior of the discharge ordraft pipe of the system and exhaust the combined current of air and steam into an expansion and condensing chamber.

My invention comprises certain improvements in the construction which renders the device more eiiicient in its work and more perfectly adapts the same to ycommercial purposes.

These improvements will appear in the following description and be particularly pointed out in the claims.

Reference being made to the accompanying drawings, wherein like letters refer to like parts throughout the several views, Figure 1 is a side elevation of a system of dispatchtubes equipped with my improvements. Fig.

2 is-a longitudinal vertical section ofa portion of the draft-pipe in workin g position, and Fig. 3 is a similar view showing the detachable section of the saine removed. Fig. 4 is a section on the line X X of Fig. l.

A A A" represent the floor-levels of a buildin ,lg B B" C CD E represent the system of pneumatic tubes, and F one of the dispatchcarriers.

G is a detachable section of the draft-pipe 3 B, fitting annular seats G in annular cappieces II H, .which are seeuredto the opposing ends of the two sections of the draft-pipe l li. The cap-pieces H and ll are clamped cndwise against the section Gto secure the pipe are detachably connected byan ordinary valve-nut and screw-thread M M.

L is a hand-valve in the steam-pipe. The section B of the draft-tube located in advance of the steam-nozzle is of relatively i small diameter as compared with the section B', and the connecting cap-section Il is of conical form. The contracted section discharges into an enlarged expansion and con-b densing chamber N, which connects with an ordinary chimney or stack P. The steam is blown from the nozzle L through the contracted section B with great force, creating afer-ced draft or current of air in the dispatch-tubes. The steam on its passage into the chamber N is suddenly permitted to expand and then 4to condense, forming a vacuum, which greatly increases the strength of the current of air in the dispatch-pipes. By the use of the contracted section B, which the steam andthe induced current of' air completely fills, any back-current from the discharge end or stack isprevented.

It is evident that the section G, containing the steam-nozzle, is readily detachable from the other sections of the draft-pipe by unscrewing the valve-nut, removing the draw-' bolts, and springing the section B backward.

The advantage ot the detachable section and its connecting cap-plates is that the parts are easily and cheaply made in form for ready application to old or new plants, and ready access is thereby afforded at any time to the .parts most likely to get out of 'order for inspection and repair.

The dispatch-tubes and the receiving-boxes may be made of any suitable material and require no special skill for their construction. The detachable section, its cap-pieees,'and the steam-nozzle are the only parts requiring any special fitting., Hence these parts, together' with the dispatch carrier or bucket, may be IOO made and supplied to the trade ready for in` corporation into Working plants by any ordinary mechanic. Y

The advantage gained in the action over the construction shown in my former application is a stronger current of air with the use of less steam. In this device, as well as in the former application, the use of the simple steam-jet nozzle is a very important gain over prior constructions, not only in thepoint of simplicity of structure, but in the point of economy of steam. An extremely small opening is sufficient to give all the draft required on a considerable system of pipes.' I have found by actual experience with .the construction herein described that a steamy-jet nozzle having an opening of three thirty-seconds of an inch is sucient for athree-tloor system of pipes, and that the amount of steam required is so small that it is unappreciable on the steam-gage of the boiler. y v

It will 4be understood that the chimney or 'stack P might oi' itself serve as theexpansion -and'condensing chamber andserve as the mechanical equivalent of the section or chamber N of the draft-pipe.

What I claim, and desire to secure 'by Letters Patent of the United States,is as follows:

1. In a pneumatic dispatch system,-the combination, with a draftpipe constructed with a discharge-section of relatively large diameter andwith a conmeeting-section of relatively small diameter, of a steam-supplypipe having its discharge-nozzle inside the draft-pipe, with its discharge -in the mouth of the connecting-section, whereby the connecting-section is made to e'xcludeall back-current and the discharge-section'is made to atord an expansion and condensing chamber for the steam, substantially as and for the vpurpose set forth. 2. A'titting for taining a steam-nozzle provided with means for detachably connecting the same with a steam-supply pipe, a pair ot flanged cap-sections tittng the.- removable section,

tions of the draft-pipe, and draw-bolts and nuts for securing,r the removable section in position, the bolts Working' through holes in the tianges of said caps,substantially as described.,

. adapted to be permanently secured to adjacent secpneumatic dispatch-tubes, ,comprising a removable section of pipe con- 

